Double negative metamaterial applications in modified log-periodic arrays for wideband pulse radiation

In ultra-wide bandwidth (UWB) communication systems, UWB pulses are used for information propagation. A log-periodic dipole array (LPDA) antenna, in spite of its wide bandwidth, is not a suitable candidate for UWB pulse radiation because of its severe frequency dispersion [1]. In [2], we proposed a modified LPDA that could potentially deal with this problem. By applying metamaterial-based phase shifters to adjust the phase centers of the radiating elements, over 90% fidelity between the transmitted pulse and the antenna reference pulse was achieved for a 10 element LPDA (Without the proposed modifications, the fidelity was only 64%. The fidelity improvement with these phase shifter modifications increases significantly as the number of radiating elements in the LPDA is increased). In [2], the focus of the efforts was mainly on the time domain pulse fidelity. Investigation of the LPDA antenna characteristics, such as return loss, gain and far field pattern shows that the modified LPDA is slightly inferior to the corresponding regular LPDA in the low frequency range of its overall bandwidth.